Non cross-linked block polyetherester, preparation and uses

ABSTRACT

The present invention relates to a non crosslinked block polymer. It also relates to a process for the preparation thereof and to the use thereof particularly in pharmaceutical compositions. The block polymer according to the invention contains sequences of polyethylene glycol linked to sequences of polyester and/or polycarbonate. The polyester sequences are selected in particular from polyfumarate, polymaleate and polysuccinate sequences.

TECHNICAL FIELD

The present invention relates to a non crosslinked block polymer.

It also relates to a process for the preparation thereof and to the usethereof particularly in pharmaceutical compositions.

BACKGROUND

The block polymer according to the invention contains sequences ofpolyethylene glycol linked to sequences of polyester and/orpolycarbonate. The polyester sequences are selected in particular frompolyfumarate, polymaleate and polysuccinate sequences.

The most advantageous polyester sequences according to the presentinvention are polyfumarates and polysuccinates.

Polysuccinates and polyfumarates have been described in patentapplication EP0043976 and have already been tested for their use inpharmaceutical compositions but were ruled out because of their highlyhydrophobic nature and their poor biodegradability.

OBJECTS OF THE INVENTION

Nevertheless, the Applicant company has succeeded in developing polymerscontaining said polyesters which are particularly suitable for use inpharmaceutical compositions.

The Applicant company has, in fact, discovered that the insertion ofhydrophilic sequences of polyethylene glycol polymers into chains ofpolyfumarate, polysuccinate and polymaleate improves thebiocompatibility of said polymers whilst reducing the toxicity thereof.

DETAILED DESCRIPTION

The block polymer according to the present invention has the followinggeneral formula (I):

—[Pa—(Pb—Pc)_(s)—Pa′—Pd—Pe]_(z)

wherein:

z=1 to 20,

s=0 to 25,

Pa represents:

—[COA—COOB]—_(t)

 where:

t=1 to 150, and

A represents CH═CH or CH₂—CH₂

B represents (CH₂)_(n)—O— where n=1 to 8,

Pb and Pd, each independently, represent:

—[COO]—_(x)

where x=0 or 1;

Pc and Pe, each independently of one another, represent:

[RO]_(u)

 where:

u=0, to 150, and

R represents an alkyl, cycloalkyl, alkenyl, alkynyl or aryl group,optionally substituted,

Pa′ represents

—[COA—COOB′]—_(t′)

where A has the same meaning as above

B represents (CH₂)_(n)O, where n =0 to 8 or [RO]_(u), R and u beingdefined as above,

and t′=0 to 150;

provided that if s=0, t′=0, x=0 and u=0 then B does not represent(CH₂)₄O if A is CH₂CH₂.

The weight-average molecular mass of the polymer is in the range 2,000daltons to 300,000 daltons.

The polyethylene glycol (PEG) sequences introduced into the polymersaccording to the present invention may be linked either directly to thepolyesters or by way of polycarbonate linkages.

The advantage of introducing PEG by way of polycarbonate linkages liesin the fact that the degradation of the polymers may be modifieddepending on the number and length of the polycarbonate sequencesintroduced into the polymer.

The presence of polycarbonate sequences has the effect of retarding therate of degradation.

Thus, the polymers according to the invention allow great flexibility interms of the choice of their biodegradability and hydrophilicproperties. In fact, it is possible to modify the biodegradability andhydrophilic properties of the polymer by altering:

the number of polycarbonate sequences and the number of PEG sequences ineach unit of the polymer,

the length of the hydrophobic and hydrophilic sequences in each unit ofthe polymer,

the length of the polymer.

The presence of hydrophilic PEG increases the water solubility of thepolymer whilst reducing its immunogenicity. Moreover, the introductionof PEG sequences as described by M. NAGATA et al. in PolymerInternational, Vol. 42, permits better biodegradability of thepolyfumarates and polysuccinates. In fact, for the same weight ofpolymer, the biodegradability is greater in the presence of PEG.

The polymers according to the present invention may have a very highmolecular weight, from 20,000 daltons upwards, whilst remaining solubleand biodegradable. Said high molecular weight polymers may beconcentrated on tumours by targeting the tumour cells by an effect knownas “Enhanced Permeability Retention Effect” (EPR). In fact, the vascularwalls of tumour cells are more permeable to macromolecules than thevascular walls of healthy cells.

The proportion of PEG sequences in the polymer also makes it possible toprepare soluble or insoluble polymers which may be used as supports foractive principles in pharmaceutical compositions or for antigens invaccines. Said polymers may, therefore, be used in the formation ofimplants, microspheres, microparticles or nanoparticles in combinationwith active principles. The nanoparticles will be composed of polymerswith superior biodegradability in order to obtain more rapid release ofthe active principle. The implants, microspheres or microparticles willallow controlled release of the active principles.

The polymers according to the invention may also be conjugated with anactive principle. By way of example, these active principles may beselected from anti-inflammatories, anti-tumour agents,immunosuppressants, anti-thrombotics, neuroleptics, anti-depressants,anti-hypertensive agents, peptides, proteins, particularly cytokines,nucleotides, or a non-toxic salt of said substances.

According to a preferred embodiment of the conjugated polymer accordingto the present invention, a polymer containing a polyfumarate sequence(A equals CH═CH) may be linked directly or via a polymeric or peptidearm to an active principle by a covalent bond. Examples of activeprinciples include anti-tumour agents such as taxol, cis-platins anddoxorubicins.

The invention also relates to a process for the preparation of the blockpolymers having the general formula (I). This process is characterisedin that polyester sequences are polymerised with polyethylene glycolsequences and in that, optionally, polycarbonate sequences areintroduced into the polymer

According to a preferred embodiment of the process according to theinvention, polyester sequences are prepared by polycondensation ofdicarboxylic acid with diols. The introduction of the carbonatesequences may be carried out in the following manner: the terminalhydroxyl groups of a monomer or of an oligomer with a bis-hydroxy endgroup are converted to an activated derivative by reaction with acompound having the formula:

X—CO—X

where X represents Cl or imidazole.

These activated derivatives react with hydroxyl compounds to obtaincarbonate groups.

By using the reagents in a stoichiometric quantity, it is possible toobtain polymers with a high molecular weight. To this end, it isimportant to have good equivalence between the COX end groups of theactivated oligomer and the OH end groups of the diols. In fact, forpolycondensation reactions (assuming that the yield of the reaction is100%), the molecular mass by weight is given by the equation:

X_(n)=(1+r)/(1−r)

where X_(n) is the average degree of polymerisation and

r is the ratio of complementary functional groups during the reaction.

The invention also relates to the use of a block polymer having thegeneral formula (I) in pharmaceutical compositions. However, saidpolymers are not limited to such a use. They may be used in all fieldsrequiring controlled biodegradability, for example, in agriculture.

The invention will be better understood by means of the followingnon-limiting examples.

EXAMPLE 1 Preparation of a Monocarbonate Block Polymer

A mixture of 0.34 ml (1.96 mmole) of ethyl diisopropylamine and 1.97 g(0.98 mmole) of a polyethylene glycol having a molecular weight of about2000 daltons (PEG 2000) in 4 ml of chloroform was prepared. This mixturewas added dropwise to a solution of 20% COCl₂ (phosgene) in toluene (2.4ml, 4.91 mmole), kept in a cooling bath at 0° C. under nitrogen, and 15minutes after the addition of the COCl₂ the remaining COCl₂ was removedby means of a stream of nitrogen for 30 minutes.

The solution was stirred by means of a magnetic stirrer and the solutionwas allowed to reach a temperature of 5° C.

A solution of PBS 3920 (3.85 g, 0.98 mmole) of ethyl diisopropylamine(0.34 ml, 1.96 mmole) and dimethylaminopyridine (0.12 g, 0.88 mmole) in21 ml of chloroform was added dropwise to said reaction mixture.

The reaction mixture was taken out of the cooling bath and the solutionwas stirred for 12 hours. The organic solvents were evaporated and theproduct was dried under vacuum.

The polymer obtained had an intrinsic viscosity in chloroform at 30° C.of 0.26 dl/g. It contained 33.7 wt. % of PEG. It had the general formula(I) above in which: Pa=—[COA—COOB]— where A=CH₂—CH₂, t=23, B=(CH₂)₄O,s=1, Pb=COO, Pc=[RO]_(u) where R=CH₂—CH₂ and u=45.5 and z=about 5.

EXAMPLE 2 Preparation of a Monocarbonate Block Polymer

A solution of 2 g of PBS 3920 (0.51 mmole), 180 mg (0.55 mmole) ofcarbonyl diimidazole and 2 g (0.5 mmole) of PEG 4000 was kept undernitrogen at a temperature of 60° C. in 15 ml of chloroform for 6 days.

The polymer was obtained by precipitation in ether.

The intrinsic viscosity in chloroform at 30° C. of the polymer obtainedwas 0.32 dl/g. The polymer contained 50 wt. % of PEG. It had the generalformula (I) above in which: Pa=[COA—COOB]t where A=CH₂—CH₂, t=23,B=(CH₂)O, S=1, Pb=COO, Pc=[RO]_(u) where R=CH₂CH₂ and u=91 and z=about4.

EXAMPLE 3 Preparation of a Monocarbonate Block Polymer

A solution of 1 g of PBS 10.034 (0.51 mmole), 129 mg (0.39 mmole) ofcarbonyl diimidazole and 0.39 g (0.09616 mmole) of PEG 4000 was kept at60° C. in 15 ml of chloroform for 6 days.

The product was obtained by precipitation in ether.

The intrinsic viscosity in chloroform at 30° C. was 0.36 dl/g. Thepolymer contained 36.7 wt. % of PEG. It had the general formula (I)above in which: Pa=[COA—COOB]_(t) where A=CH₂—CH₂, t=59, B=(CH₂)₄—O,Pb=[COO], Pc=[RO]_(u) where R=CH₂CH₂ and u=91 and z=about 2.

EXAMPLE 4 Preparation of a Polyester

4.7 g (48 mmoles) of maleic anhydride, 4.1 ml (46 mmoles) of butandioland 8 g of PEG 4000 (2 mmoles) were stirred under nitrogen at atemperature of 200° C. for 24 hours. Nitrogen was bubbled through thesolution in order to remove the water. The product was cooled undervacuum and recovered.

The polymer thus obtained had an intrinsic viscosity in chloroform at30° C. of 0.38 dl/g. It contained 52 wt. % of PEG. It had the generalformula

MORE DETAILED DESCRIPTION OF THE INVENTION

that is, the general formula (I) above is as follows: Pa—Pa′ wherePa=[COA—COOB]_(t)

where A=CH═CH,

B=[CH₂)_(n)O where n=4

t=47

Pa′=[COA—COOB′]_(t′)

where A=CH═CH,

B′=(CH₂—CH₂)O

t′=47

EXAMPLE 5 Preparation of a Polyester

34.9 g (0.3 mole) of fumaric acid, 21.03 ml (0.231 mole) of butandioland 48 g (0.08 mole) of PEG 600 were stirred under nitrogen at atemperature of 200° C. for 24 hours. Nitrogen was bubbled through thesolution in order to remove the water. The product was cooled undervacuum and recovered.

The polymer thus obtained had an intrinsic viscosity in chloroform at30° C. of 0.23 dl/g. It contained 54 wt. % of PEG. It had an identicalgeneral formula to that of example 4.

EXAMPLE 6 Preparation of a Polymer From a Monoester Diol

45.31 ml (504.8 mmoles) of butandiol were added to 5 g (50.48 mmoles) ofmaleic anhydride. The solution was stirred at a temperature of 180° C.under nitrogen for 5 hours. The excess butandiol was then distilledunder vacuum (0.1 torr) and the oily residue was recovered by,dissolution in chloroform, extraction by means of sodium bicarbonate and0.1 mole of hydrochloric acid. The residue was dried over sodiumsulfate, evaporated to dryness under vacuum and kept under high vacuum(0.05 torr) until a constant weight was obtained. The yield was 80%.

The NMR spectrum of the product showed the following structure:

HO—CH₂—CH₂—CH₂—CH₂—OOC—CH═CH—COO—CH₂—CH₂—CH₂—CH₂—OH

EXAMPLE 7 Preparation of a Polymer With a Bicarbonate Unit

0.34 ml (1.96 mmole) of ethyl diisopropylamine and 0.588 g (0.98 mmole)of PEG 600 were mixed in 4 ml of chloroform. This mixture was addeddropwise to a solution of 20% COCl₂ (phosgene) in toluene (2.4 ml, 4.91mmole), cooled to a temperature of 0° C. under nitrogen, and 15 minutesafter the addition the excess COCl₂ was removed by means of a stream ofnitrogen for 30 minutes.

The solution thus obtained was added dropwise to a solution of 0.254 g(0.98 mmole) of the diester obtained in the previous example, 0.34 ml(1.96 mmole) of ethyl diisopropylamine and 0.12 g (0.98 mmole) ofdimethyl aminopyridine in 21 ml of chloroform cooled to 15° C. in acooling bath. The solution thus obtained was agitated under nitrogen for3 hours then diluted with 5 volumes of chloroform. The solution waspurified by extraction with sodium bicarbonate and 0.01 mole ofhydrochloric acid.

The residue was then dried over sodium sulfate and evaporated to drynessunder vacuum and kept under high vacuum (0.05 torr) until a constantweight was obtained.

The polymer thus obtained had an intrinsic viscosity in chloroform at30° C. of 0.90 dl/g. It contained 70 wt. % of PEG. The product wassoluble in chloroform and in water. It had the formula (I) above inwhich:

EXAMPLE 8

a) Synthesis of PBS With a bis-Hydroxy End Group

A solution of 1,4-butandiol (29.74 g, 0.33 mole) was prepared inalcohol-free CHCl₃ (stabilised with amylene) and dried over CaH₂. Afterthe solution had been decanted, 43.98 g (0.30 mole) of (recentlydistilled) succinyl chloride were poured dropwise into this solution,with stirring.

The reaction mixture was then kept at 0° C.-5° C. in an ice bath. Duringthe reaction, N₂ was bubbled through the mixture to remove the HClformed. When the addition had ended, the mixture was heated to 60° C.until there was no more HCl in the outflowing N₂.

A small quantity of the reaction mixture (5 ml) was taken as a sample,diluted with CHCl₃ (4 volumes), extracted with a saturated solution ofNaHCO₃ then with distilled water. Finally, the organic phase was driedover anhydrous Na₂SO₄. The product was recovered by evaporation of themajority of the solvent under reduced pressure and by precipitation withEt₂O.

The product was characterised by its NMR spectrum and by chromatographicanalysis.

The results showed a PBS with a bis-hydroxy end group having anumber-average molecular mass of 2000.

b) The reaction residue was mixed with a solution of PEG 2000 (70 g) inCHCl₃ (stabilised with amylene) (130 ml) dried beforehand over CaH₂, andthe mixture was divided into 2 equal parts. The first part of thesolution was treated with N-ethyl diisopropylamine (29 g, 0.224 mole),and a solution of phosgene (20% in toluene) (17.84 ml, 0.28 mole) wasadded dropwise. The mixture was kept at 0° C.-5° C. in an ice bath andunder an N₂ atmosphere. The excess phosgene was drawn off by bubbling N₂through for 30 minutes, 15 minutes after the end of the addition. Thesecond part of the solution was treated with N-ethyl diisopropylamine(29 g, 0.224 mole) and 4-dimethylaminopyridine (12.22 g, 0.1 mole). Thefirst part of the solution, treated with phosgene, was added dropwise tothe second part of the solution with stirring and under a nitrogenatmosphere, keeping the temperature at 0° C.-5° C. in an ice bath. Theproduct was isolated using the procedure of example 8. The polymerobtained (115 g, 86.7%) was characterised by intrinsic viscosity (0.86dl/g in CHCl₃ at 30° C.) and by NMR spectrum; this polymer contains 60%of PEG, having a structure represented by formula I in which

EXAMPLE 9

The method of operating of example 9 was followed in which 43.22 g (0.30mole) of fumaryl chloride were used instead of succinyl chloride. Thepolymer obtained (110 g, 83%) was characterised by intrinsic viscosity(0.98 dl/g in CHCl₃ at 30° C.) and by NMR spectrum; this polymercontained 51% of PEG residue and had a structure represented by formulaI in which:

EXAMPLE 10

A solution of PBS with a bis-hydroxy end group was prepared, isolatedand characterised as in example 10 a). Then, as in example 8, using0.588 g of PEG 600 in CHCl₃ (stabilised with amylene) dried beforehandover CaH₂ instead of 1.96 g (0.98 mole) of PEG 2000 and 1.96 g (0.98mole) of PBS with a bis-hydroxy end group instead of 2.54 g of diester,0.32 g (81%) of a polymer were obtained having an intrinsic viscosity of0.64 dl/g (in CHCl₃ at 30° C.) and having 60% of PEG residue with astructure according to formula I in which:

What is claimed is:
 1. Non crosslinked block polymer having the generalformula (I) [—Pa—(Pb—Pc)_(s)—Pa′—Pd—Pe]_(z) wherein: z=1 to 20, S=0 to25, Pa represents: —[COA—COOB]_(t)—  where: t=1 to 150, and A representsCH═CH or CH₂—CH₂ B represents (CH₂)_(n)—O— where n=1 to 7, Pb represents—[COO]—_(x) where x=0 or 1, Pd represents: —[COO]_(y)— where y=0 or 1provided that if s=0 or x=0 then y=1, and if y=0 then s≠0 and x=1; Pcand Pe, each independently of one another, represent: [RO]_(u)  where:u=4 to 150, and R represents an alkylidene, Pa′ represents—[COA—COOB′]—_(t) where A has the same meaning as above B′ represents(CH₂)_(n)′O, where n′=1 to 7, and t′=0 to 150 the weight-averagemolecular mass of the polymer being in the range 2,000 daltons to300,000 daltons.
 2. Non crosslinked block polymer according to claim 1,wherein, R represents —CH₂—CH₂—.
 3. Non crosslinked block polymer havingthe general formula (I) as defined in claim 1, having a molecular massgreater than 20,000 daltons whilst remaining soluble and biodegradableand targeting tumour cells by an EPR effect.